As markers for definitive diagnosis of multiple sclerosis (MS), oligoclonal bands detected in cerebrospinal fluid, and the IgG index for evaluation of quantitative IgG changes in serum and spinal fluid, are used at present. However, these markers are not MS-specific, and patients clinically diagnosed with MS are negative for the markers in many cases. Therefore, a sufficient diagnosis cannot be made by using these markers only (Non-patent Document 1). A high serum antibody titer of anti-aquaporin 4 antibody in patients with neuromyelitis optica (NMO: which is currently recognized as the different disease from MS) (Non-patent Document 2), which was previously included in MS, is also available as a disease state-associated marker. However, NMO is regarded as different disease at present. Moreover, some patients without detection of the above-mentioned antibody meet diagnostic criteria for NMO, others with detection of it cannot meet the criteria. Thus, diagnosis by comprehensive judgment with an additional diagnostic marker(s) is strongly demanded. In addition to the above markers, MRI findings are taken into account for differential diagnosis of multiple sclerosis and neuromyelitis optica. The presence of cells (monocytes, polymorphonuclear leukocytes and the like) in cerebrospinal fluid, a low glucose level (in bacterial, tuberculous and fungal meningitis and the like) and the like are main criteria for meningitis, meningoencephalitis, encephalitis and encephalopathy, but these examination findings are often not obvious in meningitis, meningoencephalitis, encephalitis and encephalopathy. Moreover, there is no molecular marker available for the diagnosis.
In many cases of multiple sclerosis and neuromyelitis optica, exacerbation of functional impairment proceeds while relapse and remission are repeated after definitive diagnosis, or, in some cases, the disease activity is increased without remission, causing continuous exacerbation of functional impairment. In the acute management of these diseases, it is primarily important to evaluate and diagnose the disease states and provide treatment as soon as possible to prevent exacerbation of the functional impairment during acute relapse or increased disease activity. The disease activity is commonly evaluated using MRI. However, facilities where MRI scan is available are limited, and, even among such facilities, there are only a more limited number of facilities where the scan can be carried out emergently. Besides MRI, detection of myelin basic protein (MBP) in the spinal fluid is sometimes used for the diagnosis of relapse (Non-patent Document 3), but the sufficient diagnosis cannot be made by using it because it lacks specificity. There is no objective indicator for diagnosing the disease condition of meningitis.
Patent Document 1 describes a method in which a low level of plasma Crtac1 protein is used as an indicator for detection of cerebral infarction or identification of the type of cerebral infarction. However, the document does not disclose at all a method for early definitive diagnosis of a neurological disease accompanied by at least one of inflammation and demyelination, such as multiple sclerosis.